When pop stars Mariah Carey, Beyoncé, Nelly Furtado and 50 Cent recently said they'd renounced millions of dollars they'd received for performing for members of Libyan strongman Moammar Kadafi's family, they drew attention to a growing and controversial cultural phenomenon: celebrity artists being hired by rich, powerful and sometimes disreputable clients to play at private or semi-private functions.

From flashy hotel openings to wedding receptions, upscale bat mitzvahs and Caribbean bacchanalias, brand-name musicians, Hollywood actors and other celebrities are increasingly renting out their talents, or simply their crowd-drawing presence, for under-the-radar engagements.

Despite the potential ethical breaches, and the risk of tainting their public images, big stars likely will continue to be tempted by fat fees and all-expense-paid trips by private jet to a remote tropical island or luxury resort. Today's free-spending clients include Fortune 500 corporations, Wall Street tycoons and nouveau-riche developing-world businessmen.

Some of these artists may be motivated largely by money and are ignorant of, or indifferent to, political concerns. Others like Sting, who performed at a 2009 concert arranged at the behest of the daughter of Uzbekistan dictator Islam Karimov (known for jailing dissidents and other human rights abuses), see themselves as cultural ambassadors opening new communications channels into closed societies.

Top stars' managers take care to protect their artists' reputations by pre-screening clients, "so they know they're not getting a briefcase of cash that wouldn't be clean, wouldn't be legal and would cause them all kinds of problems," said Bob van Ronkel, who runs a Moscow-based business that arranges for actors and musicians to appear at charity events, concerts and other activities, frequently in Russia and Central Asia.

But that can be difficult if the client is using a third-party intermediary or hiding behind a pseudonym, as one of Kadafi's sons is known to do, Van Ronkel said.

That was the explanation put forward by Carey last week when she renounced the reported $1 million she earned for giving a private 2008 New Year's Eve concert bankrolled by a member of the Kadafi family.

"I was naive and unaware of who I was booked to perform for," the singer, who has a substantial record of philanthropic activities, said in a statement. "I feel horrible and embarrassed to have participated in this mess. Going forward, this is a lesson for all artists to learn from. We need to be more aware and take more responsibility, regardless of who books our shows."

A few days previously, Furtado, the Canadian pop chanteuse, had announced in a Twitter message that she planned to give away the $1 million she made playing a 45-minute show for the Kadafi clan at an Italian hotel in 2007. She did not specify where the money would go.

Beyoncé said in a statement that she hadn't realized who was picking up the tab for a Kadafi-sponsored private party. "Once it became known that the third-party promoter was linked to the Kadafi family, the decision was made to put that payment to a good cause," the statement read. The singer said she already had donated the money she earned to Haitian earthquake-relief efforts.

Then this week rapper 50 Cent said that he, too, would donate to charity the money he'd earned performing several years ago at yet another private event linked to Kadafi family members.

Chris Palmer, a former vice president of progressive music and senior vice president of marketing for Warner Bros. Records, said that many artists typically are disconnected from who they are performing for, or for what reason, being more interested in putting on a good show.

"Some of the artists are so focused on being good entertainers, they're oblivious to the politics," said Palmer, now an assistant professor and program director for Arts Presenting at the University of Miami Frost School of Music. "Not all artists are as politically aware as Bruce Springsteen, Sting or Bono. It's a responsibility of their agents, and support staff, and the people around them to make that kind of call."

But even booking agents and managers may not know who'll show up at a gig until after it's planned. Van Ronkel said that Russian Prime Minister Vladimir Putin turned up on short notice last December at a charity event, billed as aiding hospitals for children with cancer, at which Kevin Costner performed with his band. Putin sang "Blueberry Hill" and played a grand piano.

At the time, Van Ronkel said, no one in his entourage was thinking about politics. "Governments think politics," he said, "but most of us are thinking, 'Wow, Kevin's here performing.'"

The event has subsequently drawn Russian media attention after the mother of a girl with cancer wrote an open letter implying the event may have benefited Putin's public image more than the children.

Sam Craig, director of the entertainment, media and technology program at New York University's Stern School of Business, said that although such private performances can backfire on an artist, the risk is minimal — at least in commercial terms. In a culture in which celebrities becoming tangled in a fracas of one kind or another is commonplace, these episodes don't tend to leave any lasting damage, he said. The fact that performances of this kind, by nature, fly under the media radar also lessens the danger of exposure.

"If it really blows up, you can just say you made a mistake, and 'I'll give the money to charity,' or something," Craig said. "There's got to be a pattern of something before fans flee."

Sting, for his part, offered no public mea culpa for playing the Uzbekistan concert, for which the former lead singer of the Police, well-known for his concert work on behalf of human rights and ecological causes, reportedly pocketed as much as 2 million British pounds. Sting later said he was "well aware of the Uzbek president's appalling reputation in the field of human rights as well as the environment. I made the decision to play there in spite of that."

"I have come to believe," the rock star declared, "that cultural boycotts are not only pointless gestures, they are counterproductive, where proscribed states are further robbed of the open commerce of ideas and art and as a result become even more closed, paranoid and insular."

Still, boycotts, whether formal or informal, may cause a celebrity to think twice. Last year Jennifer Lopez called off an appearance at a luxury hotel in the breakaway Turkish north of Cyprus when a furor over the gig erupted between Greek and Turkish Cypriots in that divided Mediterranean island. The pop star and "American Idol" judge reportedly would've earned $3 million for the gig. A statement posted on Lopez's website said the singer's decision "reflects our sensitivity to the political realities of the region."

Artists may find themselves standing on the wrong side of an ethical line if political circumstances shift suddenly. Although widely reviled for decades, the Kadafi regime had marginally improved its international standing in recent years after Libya renounced its pursuit of nuclear weapons. The regime's brutal crackdown this winter has restored its pariah status; that has drawn renewed scrutiny to foreigners dealing with the Kadafis.

Raul Pacheco and Ulises Bella, members of the left-leaning, politically activist L.A. band Ozomatli, said in an interview that the group had debated long and hard about whether to participate in foreign concert tours sponsored by the U.S. State Department in countries such as Myanmar, also known as Burma, which for decades has been ruled by a military junta.

In such situations, the ethical choices facing artists can be complex, the band mates suggested. Speaking of Furtado's recent about-face, Bella said, "She got dissed, [but] I'm thinking, 'Wow, she's giving $1 million to somebody that can use that money.'"

Pacheco said that, "whatever the agendas of most governments are, I think people getting together is very important."

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